One of the typical questions that people ask me when talking about the smarthome installation is “What happens in case of power outage?”, trying to target some weak spots of the solution.
Well, usually the simplest answer is that in the event of power loss all happens the same as with any conventional “dumb” home install. But, if we look at some details we might discover that this is not entirely truth. Let’s have a look at some typical scenarios and how can we mitigate the impact.
With the basic stuff like lights, blinds or ventilation control, you might not be bothered that the controlling system goes down after any electricity failure. However, as soon as your smarthome integrates things like burglar alarm, smoke or water leak alarm, cctv or keyless access, you might need to have these things working with some kind of power back-up.
In my installation with Loxone I did quite extensive research and gone through various solutions before I got to the one I am happy with. Given the fact that Loxone does not have any custom device to maintain uninterruptible power supply, you’ll need to look elsewhere for suitable solution.
Standard 230V UPS solution
One of the easiest solutions, people usually tend to, is purchasing one of a small free-standing UPS with 230V output. Basically, this is not that bad idea, especially when this power backup is also feeding your home network (router, switch) and potentially other stuff like NAS and IP cameras.
The advantages here are that you do not have to take care about the batteries at all, charging and the whole battery management is integrated in the built-in electronics. If you purchase some of the better models, you might get additional protection between the incoming utility power and sensitive electronic equipment. Also, for some models the status can be read by Loxone and follow-up actions triggered in case of low battery capacity, battery failure and others.
The main drawback here is that conventional UPS systems do have lower efficiencies and a lot of energy is wasted in the dual electricity conversion (230VAC to low Voltage DC and then back to 230V AC). On a top of that, the output of the conventional UPS will be again going to another PSU (or multiple) feeding the Loxone infrastructure, which represents another drop in the efficiency. Now, you might think that we can neglect these energy losses (even if this is 24/7 consumption), but in the event of power outage, when we switch to battery mode, the unnecessary conversion to 230 AC and then back to 24 VDC reduces the potential up-time. Try to run your UPS without any load to see how long does it take to discharge the batteries just with the DC to AC built-in converter on. Then you can add the idle consumption of the Loxone PSU and the whole power wastage is there. Wouldn’t be nice to feed the Loxone infrastructure with the DC battery voltage directly? If you are preferring longer battery time, standalone conventional UPS with 230V output is probably not recommended.
- Easy setup and integration
- Surge protection or even ‘electrical firewall’ depending on the device type
- Can back-up other devices like network hw (switch, router or nas)
- Disputable complexity level of status reading
- Energy loss through multiple conversions (mains – battery – mains – 24VDC for Loxone)
- Single point of failure (smarthome control, home network, NAS, cameras, …) unless you have multiple units
Power supply with UPS function
The other option how to protect the system against power cut-off are PSUs with integrated UPS function. Unlike the Standard 230V UPS, these provide direct DV output from the batteries in case of power loss. This means that there is no conversion back to 230V and thus no associated efficiency loss. This would be the ideal option if …
I came across three types of such UPS power supply units. The common limitation there is the following. All devices I have tested do have just one integrated PSU that feeds both output channels. Typically, you would need an output (say CH1) that has DC 24V for the Loxone infrastructure, and then other one (CH2) to connect to your batteries. To maintain proper charging of the batteries, the output of CH2 needs to be higher than 24V, usually 27.48V (depending on the battery type). But because the two output channels in these units are linked to one integrated PSU, what can be achieved is either that you run all your equipment on 27.48 or more Volts and your batteries will be charged, or you set properly 24V as the DC output for both, and your battery will never charge. There is no way setting the voltage differently per channel, which was my main complaint.
Tested PSUs were:
- MEAN WELL PSC60B
- MEAN WELL PSC100B (and I am sure that it will be the same for others like DRC100)
- ADELSYSTEM CBI245A DC UPS
I have contacted both manufacturers and they just confirmed my observations as “by-design” with responses in the same manner.
“The voltage of CH2 is the same as the CH1, because it is provided by the CH1 with the circuit of the limited charge current. I think it is normal for the UPS system. The voltage will be provided by the battery when the AC power disappears. The voltage range of the battery is about 24~27V. So I think your load must accept the voltage range.”MEANWELL SUPPORT
“… the output to the load can be adjusted from 22 to 28.8 V DC and the output voltage is same for both load and batteries.”ADELSYSTEM
The next question then needs to be: “Is safe to run Loxone on 27.48 Volts (or even a bit more)?”
I did contact Loxone support with this regard and was not surprised that it is not recommend. In their response they mentioned that the tolerance level of supply voltage is +-10%, which would represent range from 21.6 V to 26.4 V=.
What does it mean then, will it survive? I personally know people that are running systems on such higher Voltage because of the limitations described above. It could probably mean slightly quicker wear of some electric parts in the system. I was not looking at the wiring of the units, but I would expect there to be some constant voltage regulator (need prove of this assumption). If so, the higher voltage would be compensated by increased heat in the units itself, and subsequently more heat in the electricity cabinet. Almost all Loxone extensions do have temperature values readable and these can be monitored.
The only bad experience I had was with one type of PIR sensor, that has been tweaked from 12V to 24V using voltage regulator and two capacitors. The fact that there were electronics relays (SSR) resulted that it burned the output channel after raising the Voltage by three Volts and you could smell this all around the house.
- Minimal space requirements in the cabinet
- Reasonable pricing level
- Two digital outputs to be integrated (depends on the type of the unit) to read the status
- PSU integrated with ups function (with all pros and cons)
- Not possible to set different voltage levels for load and batteries, so you either not charge your batteries properly or need boost the voltage output towards the load which is beyond the tolerance level
Separate DC UPS control unit
After going through the options above, here is my final solution (I am happy with).
It is Weidmüller ConnectPower DC UPS 24V. It is a DIN rail mount unit in robust metal housing that has no integrated PSU. You can buy PSU from Weidmüller to sit on the DIN rail next to it in the same design if you want to, but it works flawlessly with any other 24V DC power supply types. In my case I am using MeanWell HLG series, which is my preferred PSU type.
This DC UPS works the way that you simply connect 24V DC input from your power supply source and in normal operation it passes the Voltage through it with just minimal drop (-0.2V), so you get 23.8V on the output side. The integrated charger makes the appropriate (higher) voltage needed for successful recharge of the batteries (temperature compensated) 27.48 V @ 20°C. In the event of a mains failure (drop of the DC input voltage) the system switches instantly to battery operation. It supports batteries of the total capacity of 1.3 Ah, 3.4 Ah, 7.2 Ah, 12 Ah, 17 Ah, which is selectable with rotary switch.
It also has digital inputs that can be connected to Loxone to give you info about Normal/Battery operation, Charging the batteries and Fault alarm. It provides high degree of energy efficiency, ≥ 96% normal mode when battery is being charged, ≥ 98% normal mode when battery is fully charged and ≥ 98% in buffer mode, when running on batteries.
The price is ranking a bit higher (~200 EUR) compared to the previous PSUs with integrated UPS function, but I think it is worth considering as this device really takes care of your batteries providing the right charging voltage and keeps your output voltage to your infrastructure within the accepted voltage range. This is by far the most convenient solution as I can tell after a year of 24/7 running experience.
- Proper output voltage to load and batteries
- Three status output signals to monitor the health (normal/batt. operation, charging, fault)
- Potential good energy efficiency (depending also on the connected power supply)
- Industrial design of housing and connectors
- No integrated power supply, has to be external
- Higher price
So, if you are looking for solution that will provide you the longest battery run, this ConnectPower DC UPS 24V with some pair of good batteries and reliable PSU might be the best option. I would be more than happy to get your view on this topic so feel free to respond with your suggestions. Ideas like connection solar panels to prolong the battery run might be interesting.